Moore's Law states that the number of transistors that can be placed on an integrated circuit will increase exponentially. The statement was first made by Gordon E. Moore, co-founder of Intel, in an April 1965 paper in Electronics Magazine. Titled "Cramming more components onto integrated circuits", the article describes how Moore expects the number of transistors to double every year. In 1975 Moore adjusted this to doubling every two years. Proponents of the theory of technological singularity often cite Moore's Law to defend or support their arguments.
At a certain point Moore's Law will run up against the Heisenberg uncertainty principle. A switch will be so small it will no longer be able to retain a definite quantum state (on or off) at the same time its position was so precisely defined. Quantum computing is an attempt to bypass this problem by turning it into its own solution.
 A self-fulfilled prophecy
It should be noted that just calling something a "law" doesn't automatically mean that it ought to happen or that it must happen. It should be obvious that it is only through the everyday efforts of the people in the tech industry that current processing power "keeps up" with the law rather than because of the law—although economic predictions are routinely made in the industry on the basis of the law.
Wars, natural & economic disasters could all affect the steady fulfillment of the law (regardless of technological constrains) and nothing stops humans from regressing, slowing down, or even speeding up. E.g. how computer clock speeds steadily increased in rough accordance with the law, until stalling at about 3 GHz—meaning processor power now has to be increased through smarter designs and multiple CPU cores.